Better calibration results may be obtained by ensuring your phone’s camera is correctly calibrated. This can be done by providing it with reference white, red, green and blue colors from a known good source of sRGB colors, such as Microsoft’s Surface Book 2.
This video illustrates how to capture reference colors from a Windows 10 device. All four colors white, red, green and blue must be captured from the same device at the same brightness settings. The reference white must be captured first, as depicted in the video.